Laccase from Coriolus hirsutus as alternate label for enzyme immunoassay -Determination of pesticide 2,4-dichlorophenoxyacetic acid

A new label-laccase from the fungus Coriolus hirsutus-was applied for solid -phase enzyme-linked immunosorbent assays of the pesticide 2,4-dichlorophen oxyacetic acid (2,4-D). Two proposed assays are based on (1) competitive bi nding of antibody-laccase conjugate with immobilized 2,4-D-protein conjugat e and 2,4-D in tested sample, and (2) competition of 2,4-D and 2,4-D-laccas e conjugate for binding with immobilized antibodies. Kinetic and concentrat ion dependencies for these reactions were studied, and the ELISAs were opti mized in accordance with the data obtained. The elaborated systems permit t he detection of 2,4-D in concentrations down to 10-20 ng/mL; time of the as says is 1.5-2 h. The main advantage of the laccase label, in comparison wit h the widely used peroxidase one, lies in the lack of hydrogen peroxide fro m substrate mixture, because dissolved oxygen plays the role of oxidizer.